This protocol is supported by the Alzheimer's Disease Cooperative Study (ADCS) at the University of California-San Diego. The NIH grant number is 5U01 AG19483. The mild cognitive impairment protocol is entirely an investigator-sponsored protocol developed under the auspices of the Alzheimer's Disease Cooperation Study (ADCS, a consortium of investigators funded by the National Institutes of Aging. Pfizer/Eisai is contributing partial funding to this investigator-initiated study. The ADCS has unrestricted rights to the data and will publish the analyses from this trial as the investigators have done in all previous ADCS trials. Primary Objective: To evaluate the efficacy and safety of 1,000 IU of vitamin E bid or 10 mg of donepezil, administered daily, to delay the clinical diagnosis of Alzheimer's Disease when administerd orally, to 720 individuals with mild cognitive impairment for thirty six months. Efficacy will be determined by compairing the rate of conversion to AD for vitamin E or donepezil to that observed with placebo. Secondary Objective: To evaluate the efficacy of vitamin E and donepezil on cognition in MCI subjects. The cognitive measures will be the components of the Neuropsychological Battery (Digits Backward, Symbol Digit, a Maze, a Letter Cancellation Test, World List Recall, Immediate and Delayed Paragraph Recall a variation of the Boston Naming Test, Cagetory Fluency, and Clock Drawing) the ADAS-COG and the MMSE. The investigators will also measure global clinical and functional change utilizing the Clinical Dementia Rating Scale (CDR), a Clinical Global Impression of Change Scale designed for MCI subjects (MCI-CGIC), the ADAS- Activities of Daily Living Scale (ADCS-ADL), and the Global Deterioration Scale (GDS). A Pharmacoeconomic instrument under development by the ADAS and a Quality of Life assessment (Logsdon, 1997) will be obtained as additionaloutcome measures.